Question

A certain forest covers an area of 2400km^2. Suppose that each year this area decreases by 8.5%. What will the area be after 13 years?

Answer 1

This is like the equation of a line where y is the area, x is the time, and 8.5% is your slope.
So you have y=0.085x+b (reason why I switched 8.5% into 0.085 is because that is how you write a percent as a decimal).
So now you need to find what b is. So you know orignally the area is 2400km^2 at x=0 years (this is what it is initially).
If you plug those numbers in you have:
2400=0.085(0)+b
Then after solving for b, you can write your equation as:
y=0.085x+(whatever you found b to be)
Then plug 13 in for x and you have your answer.

Answer 2

So I am solving for y? and my slope is negative right?

Answer 3

ooops, you're right it is negative.

Answer 4

so i'm doing y=-.085(13)+2400?

Answer 5

Yep; exactly.

Answer 6

but if i round to the nearest kilometer I get 2399? is that right? I mean the first yea almost 10 percent of the forest should be gone

Answer 7

Ah, I oversimplifying the problem!

So the equation you have to use is actually A(t)=2400*(1-0.085)^t

Answer 8

i did something different now I get 2386

Answer 9

ok so 756

Answer 10

that sounds a lot better haha

Answer 11

Mhm. Sorry I have been helping some other people with linear problems so my brain is set on that right now for some reason.

Answer 12

Thank you

Answer 13

You're welcome.